1. Field of the Invention
The present invention relates generally to a power conversion apparatus.
2. Description of the Related Art
In general, to constitute a power conversion apparatus with a large capacity, the direct current (DC) sides power conversion circuits are connected in parallel. Many power conversion apparatuses are configured to decrease an impedance component and so reduce the loss. For example, it is known that a capacitor and a semiconductor element constituting a power conversion circuit are connected to a laminated conductor having a thin-plate shape to reduce an inductance component. In addition, a structure in which a plurality of inverters are connected via damping resistors to prevent ripple currents among the inverters is disclosed (for example, refer to Jpn. Pat. Appln. KOKAI Publication No. 7-123724). Further, a power conversion apparatus configured to improve the nonuniformity of the power path to realize a large current is disclosed (for example, refer to Jpn. Pat. Appln. KOKAI Publication No. 2012-95472).
However, in the case of a power conversion apparatus in which a plurality of power conversion circuits are connected in parallel, a ripple current generated in a power conversion circuit by the switching due to the pulse width modulation (PWM) control flows into another power conversion circuit. This ripple current is difficult to reduce in a power conversion apparatus configured to reduce impedance components. Therefore, the ripple current has a significant influence on the power conversion apparatus.
When components such as reactors and resistors are provided to reduce the ripple current, the power conversion apparatus becomes large. When a power conversion circuit is unitized, it is difficult to ensure sufficient space for components such as reactors and resistors in the unit.